Purpose: To determine whether airflow is required to obtain the beneficial effects of rehydration (thermoregulatory and cardiovascular) during exercise in dry heat. Methods: Ten moderately trained (VO2max = 55 +/- 8 mL/kgmin) heat acclimated males pedaled for 60 min at 60% VO2max in a hot-dry environment (36 +/- 1°C; 29 +/- 2% relative humidity) on four different occasions: 1) without rehydration or forced airflow (control trial; CON); 2) rehydrating 100% of sweat losses by ingestion of a 6% carbohydrate-electrolyte solution (rehydration trial; REH); 3) receiving airflow at a velocity of 2.55 m/s (wind trial; WIND); and 4) combining airflow and rehydration (W + R). Results: Without airflow, rehydration alone (REH) did not lower rectal temperature below CON (39.0 +/- 0.1 vs 39.1 +/- 0.1°C at 60 min; respectively). However, with airflow, rehydration reduced final rectal temperature (38.8 +/- 0.1 vs 38.5 +/- 0.1[degrees]C; P < 0.05; WIND vs W + R). In the trials with wind (WIND and W + R), skin temperature was reduced by about 0.6[degrees]C (P < 0.05), and heart rate drift was prevented. In the trials with rehydration (REH and W + R trials), cardiac output (CO2-rebreathing technique) was maintained higher than CON (16.5 +/- 0.4 and 17.0 +/- 0.7 vs 15.4 +/- 0.4 L/min, respectively; P < 0.05). Conclusion: When exercising in a hot-dry environment, airflow is required for rehydration to improve thermoregulation and cardiovascular function.
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